Water safety is a major global concern, especially in developing countries such as India and China where an estimated one billion people lack access to clean drinking water. Until now, water safety testing has required expensive, specialized equipment not accessible to the average citizen. However, a new technology developed by Waterloo researchers Simarjeet Saini and Mohammadreza Khorasaninejad is poised to change the course of water safety history.
Sponsored by a Natural Sciences and Engineering Research Council (NSERC) Discovery grant, Saini and Khorasaninejad have created a novel nano-photonic chip called a Surface Plasmon Array Sensor (SPLAS). Used with the camera and processor of a standard cell phone, the SPLAS becomes an optical sensor priced at less than $20 that can detect pathogens.
The SPLAS chip consists of an array of receptors that reflect vivid colours when lit by a simple white LED. The chip is integrated with channels that bring a water sample to the receptors. If pathogens are present in the sample, they are selectively bound to the receptors, which leads to a change in the displayed colour on the sensor, indicating that the water is contaminated. A cell phone is used to capture and analyze the sensor’s image for colour changes. Water quality data can then be transmitted using wireless networks to a central server and distributed by social media to the people that use the water source.
Saini got the idea for the sensors from butterfly wings. “I have always been fascinated by these beautiful nanostructures,” he says. Once, while viewing a butterfly wing under a microscope, he accidentally dropped some water on it and the colour changed. This got him thinking about whether he could generate structural colours in chips that would change noticeably with small surface attachments.
Current bacteria detection methods involving culture growth and lab analysis take multiple days to process. Other optical chips being researched for this purpose require expensive equipment such as spectrometers and other optical components. This new method is quick and inexpensive and uses the connectivity of cell phones to swiftly disseminate results.
The SPLAS sensor can also be used in food inspection to check for bacteria. Because the test results are available quickly, a contamination problem can be caught before the food goes out into the market.
Saini and his team are currently functionalizing the chips such that specific chips can be used to detect specific pathogens. They are also creating a lab-on-a-chip device that will take a picture of the test result colour, analyse it and send the results wirelessly to a secure server. With production scheduled to be completed in early 2014, Saini is currently seeking investors.
“No one should ever have to become sick or die from contaminated food or water,” says Saini. “This sensor could save thousands of lives.”